共查询到20条相似文献,搜索用时 31 毫秒
1.
Shuai Shi Elizabeth S. Dodds Ashley Barbara D. Alexander Anthony J. Hickey 《AAPS PharmSciTech》2009,10(1):129-137
Pharmaceutical aerosols have been targeted to the lungs for the treatment of asthma and pulmonary infectious diseases successfully.
Micafungin (Astellas Pharma US, Deerfield, IL, USA) has been shown to be an effective antifungal agent when administrated
intravenously. Pulmonary delivery of micafungin has not previously been reported. In the present pilot study, we characterize
the performance of two nebulizers and their potential for delivering micafungin to the lungs as well as the use of multivariate
data analysis for mass distribution profile comparison. The concentration of micafungin sodium increased by 21% when delivered
by the Acorn II nebulizer and by 20% when delivered by the LC Plus nebulizer, respectively, from the first to the second sampling
period. The Acorn II nebulizer delivered a fine particle fraction FPF5.8 (%<5.8 μm) of 92.5 ± 0.8 and FPF3.3 (%<3.3 μm) of 82.3 ± 2.1 during the first sampling period. For the LC Plus nebulizer, FPF5.8 was 92.3 ± 0.1 and FPF3.3 was 67.0 ± 0.7 during the first sampling period. The mass median aerodynamic diameter (MMAD) increased from 1.67 ± 0.05 to
1.77 ± 0.04 μm (Acorn II nebulizer) and from 2.09 ± 0.01 to 2.20 ± 0.01 μm (Pari LC Plus nebulizer) from the first to the
second sampling periods. These changes in MMAD were statistically significant by paired t test. Multivariate data analysis showed that this could be explained systematically by greater drug deposition on stages
with larger cutoff sizes and reduced drug deposition on stages with smaller cutoff sizes rather than multimodal deposition
or other anomalies in size distribution. 相似文献
2.
The purpose of this study was to determine if aerosol delivery of drug loaded microparticles to lungs infected withMycobacterium tuberculosis may be achieved by predicting dispersion of dry powders through knowledge of particle surface properties. Particle sizes
of rifampicin-loaded poly(lactide-co-glycolide) microparticles (R-PLGA), rifampicin alone, and lactose and maltodextrin carrier
particles (bulk and 75-125-μm sieved fractions) were determined by electron microscopy for the projected area diameter (Dp) and laser diffraction for the volume diameter (Dv). Surface energies (Y) of R-PLGA, rifampicin alone, lactose, and maltodextrin were obtained by inverse phase gas chromatography,
surface areas (Sa) by N2 adsorption, and cohesive energy densities by calculation. Particle dispersion was evaluated (Andersen nonviable impactor)
for 10% blends of R-PLGA and rifampicin alone with bulk and sieved fractions of the carriers. Dp for R-PLGA and rifampicin alone was 3.02 and 2.83 μm, respectively. Dv was 13±1 and 2±1 μm for R-PLGA and rifampicin alone, respectively, indicating that R-PLGA was more aggregated. This was evident
in Y of 35±1 and 19±6 mJ/m2 for R-PLGA and rifampicin alone. Dp for lactose and maltodextrin (sieved and bulk) was approximately 40 mm. Bulk maltodextrin (Dv=119±6 mm) was more aggregated than bulk lactose (Dv=54±2 mm). This was a result of the higher Sa for maltodextrin (0.54 m2/g) than for lactose (0.21 m2/g). The Y of bulk lactose and maltodextrin was 40±4 and 60±6 mJ/m2 and of sieved lactose and maltodextrin was 39±1 and 50±1 mJ/m2. Impaction studies yielded higher fine particle fractions of R-PLGA from sieved lactose, 13%±3%, than from sieved maltodextrin,
7%±1%, at 90 L/min. An expression, based on these data, is proposed as a predictor of drug dispersion from carrier particles.
Delivery of dry powder formulations can be achieved by characterizing particle surfaces and predicting impact on dispersion. 相似文献
3.
An investigation into the changing phytoplankton biomass and total water column production during autumn sea ice formation
in the eastern Weddell Sea, Antarctica showed reduced biomass concentrations and extremely low daily primary production. Mean
chlorophyll-a concentration for the entire study period was extremely low, 0.15±0.01 mg.m−3 with a maximum of 0.35 mg.m−3 found along the first transect to the east of the grid. Areas of low biomass were identified as those either associated with
heavy grazing or with deep mixing and corresponding low light levels. In most cases phytoplankton in the <20-μm size classes
dominated. Integrated biomass to 100 m ranged from 7.1 to 28.0 mg.m−2 and correlated positively with surface chlorophyll-a concentrations. Mean PBmax (photosynthetic capacity) and αB (initial slope of the photosynthesis-irradiance curve) were 1.25±0.19 mgC. mgChla
−1.h−1 and 0.042±0.009 mgC.mgChla
−1.h−1.(μmol.m−2.s−1)−1 respectively. The mean index of photoadaptation,I
k, was 32.2±4.0 μmol.m−2.s−1 and photoinhibition was found in all cases. Primary production was integrated to the critical depth (Z
cr) at each production station and ranged from 15.6 to 41.5 mgC.m−2.d−1. It appears that, other than grazing intensity, the relationship between the critical depth and the mixing depth (Z
mix) is an important factor as, ultimately, light availability due both to the late season and growing sea ice cover severely
limits production during the austral autumn. 相似文献
4.
Drought effects on photosynthesis of the mangrove, Avicennia germinans, under contrasting salinities
M. A. Sobrado 《Trees - Structure and Function》1999,13(3):125-130
Drought effects on leaf photosynthesis of A. germinans growing under two contrasting salinities were studied in a Venezuelan fringe mangrove. During both wet and dry seasons, severe
chronic-photoinhibition at predawn was not observed but strong down regulation occurred at midday during both seasons. Carbon
assimilation rates (A, μmol CO2 m−2 s−1) declined during the dry season from 11.9±1.8 to 7.0±1.5 and from 9.6±2.0 to 4.7±2.5 in plants from low and high salinity
sites, respectively. Changes in carbon assimilation per unit of chlorophyll (A/Chl, mmol CO2 mol−1 Chl) were from 31.6±4.7 to 20.5±4.3 and from 21.9±4.7 to 15.2±8.2 in the low and high salinity plants, respectively. Therefore,
neither changes in Chl nor seasonal differences in photoprotective down regulation could account fully for the decrease in
leaf photosynthesis during drought. A reduction in CO2 diffusion due to lowered stomatal conductance was not large enough to explain such a dramatic effect of drought on leaf photosynthesis.
Stomatal response could be mitigated by the capability of A. germinans for osmotic adjustment under high salinity and/or drought. However, this intracellular salt accumulation may reduce carbon
assimilation capacity further by decreasing the metabolism of leaf cells, increasing dark respiration and/or photorespiration.
Received: 10 June 1998 / Accepted: 5 October 1998 相似文献
5.
Metabolic hotspots at land–water interfaces are important in supporting biogeochemical processes. Here we confirm the generality
of land–aquatic interfaces as biogeochemical hot spots by extending this concept to marine beach cast materials. In situ atmospheric
pCO2, from a respiration chamber (10 cm in diameter and 20 cm high) inserted into wrack deposits, was determined using a high-precision
(±1 ppm) non-dispersive infrared gas analyzer (EGM-4, PP-systems) at 1 minute recording intervals. The wrack deposits supported
high metabolic activities, with CO2 fluxes averaging (±SE) 6.62 ± 0.88 μmol C m−2 s−1, compared to median value of 0.98 μmol C m−2 s−1 (mean 2.21 ± 1.25 μmol C m−2 s−1) for bare sand adjacent to deposits. Wrack metabolic rates ranged 40-fold across beaches, from a minimum of 0.57 ± 0.22 μmol
C m−2 s−1 to a maximum of 20.8 ± 5.04 μmol C m−2 s−1, both derived from beaches with deposits dominated by Sargassum. Rates tended to increase significantly (F test, P < 0.05) from the shoreline to reach maximum rates at about 10 m from the shoreline, declining sharply further from the shoreline,
and increased with increasing thickness of the deposits (maximum about 10 cm deep), declining for thicker deposits. Wrack
differing in composition had similar metabolic rates, although deposits consisting of a mixture of seagrass and algae tended
to show somewhat higher rates. Our results show a meter square of wrack deposit supports a metabolic rate equivalent to that
supported by 3 m2 of living seagrass or macroalgal habitat. In wrack, the marine environment provides organic material and moisture and the
land environment provides oxygen to render wrack ecosystems an efficient metabolic reactor. Intense wrack metabolism should
also be conducive to organismal growth by supporting the development of a cryptic, but diverse wrack-based food web. 相似文献
6.
We have characterized a Na+/H+ exchanger in the membrane of isolated zymogen granules (ZG) from rat exocrine pancreas and investigated its role in secretagogue-induced
enzyme secretion. ZG Na+/H+ exchanger activity was estimated by measuring Na+ or Li+ influx and consequent osmotic swelling and lysis of ZG incubated in Na- or Li-acetate. Alternatively, intragranule pH was
investigated by measuring absorbance changes in ZG which had been preloaded with the weak base acridine orange. Na+- or Li+-dependent ZG lysis was enhanced by increasing inward to outward directed H+ gradients. Na+-dependent ZG lysis was not prevented by an inside-positive K+ diffusion potential generated by valinomycin which argues against parallel operation of separate electrogenic Na+ and H+ permeabilities and for coupled Na+/H+ exchange through an electroneutral carrier. Na+- and Li+-dependent ZG lysis was inhibited by EIPA (EC50∼25 μm) and benzamil (EC50∼100 μm), but only weakly by amiloride. Similarly, absorbance changes due to release of acridine orange from acidic granules into
the medium were obtained with Na+ and Li+ salts only, and were inhibited by EIPA, suggesting the presence of a Na+/H+ exchanger in the membrane. Na+ dependent lysis of ZG was inhibited by 0.5 mm MgATP and MgATP-γ-S by about 60% and 35%, respectively. Inhibition by MgATP was prevented by incubation of ZG with alkaline
phosphatase (100 U/ml), or by the calmodulin antagonists calmidazolium (0.75 μm), trifluoperazine (100 μm) and W-7 (500 μm), suggesting that the ZG Na+/H+ exchanger is regulated by a ZG membrane-bound calmodulin-dependent protein kinase. Na+ dependence of secretagogue (CCK-OP)-stimulated amylase secretion was investigated in digitonin permeabilized rat pancreatic
acini and was higher in acini incubated in Na+ containing buffer (30 mm NaCl/105 mm KCl buffer; 6.4 ± 0.4% of total amylase above basal) compared to buffer without Na+ (0 mm NaCl/135 mm KCl buffer; 4.7 ± 0.4% of total amylase above basal, P < 0.03). EIPA (50 μm) reduced CCK-OP-induced amylase secretion in Na+ containing buffer from 7.5 ± 0.6% to 4.1 ± 0.8% (P < 0.02). In the absence of Na+ in the buffer, CCK-OP-stimulated amylase release was not inhibited by 50 μm EIPA. The data suggest that an amiloride insensitive, EIPA inhibitable Na+/H+ exchanger is present in ZG membranes, which is stimulated by calmodulin antagonists and could be involved in secretagogue-induced
enzyme secretion from rat pancreatic acini.
Received: 7 December 1995/Revised: 2 April 1996 相似文献
7.
Oze H Hirao M Ebina K Shi K Kawato Y Kaneshiro S Yoshikawa H Hashimoto J 《In vitro cellular & developmental biology. Animal》2012,48(2):123-130
Previous studies have demonstrated that oxygen environment is an important determinate factor of cell phenotypes and differentiation,
although factors which affect pericellular oxygen concentration (POC) in murine chondrogenic cell culture remain unidentified.
Oxygen concentrations in vivo were measured in rabbit musculoskeletal tissues, which were by far hypoxic compared to 20% O2 (ranging from 2.29 ± 1.16 to 4.36 ± 0.51%). Oxygen concentrations in murine chondrogenic cell (C3H10T1/2) culture medium
were monitored in different oxygen concentrations (20% or 5%) in the incubator and in different medium volumes (3,700 or 7,400 μl)
within 25-cm2 flasks. Chondrogenic differentiation was assessed by glycosaminoglycan production with quantitative evaluation of Alcian
blue staining in 12-well culture dishes. Expression of chondrogenic genes, aggrecan, and type II collagen α1, was examined
by quantitative real-time polymerase chain reaction. Oxygen concentrations in medium decreased accordingly with the depth
from medium surface, and POC at Day 6 was 18.99 ± 0.81% in 3,700-μl medium (1,480-μm depth) and 13.26 ± 0.23% in 7,400-μl
medium (2,960-μm depth) at 20% O2 in the incubator, which was 4.96 ± 0.08% (1,480-μm depth) and 2.83 ± 0.42% (2,960-μm depth) at 5% O2, respectively. The differences of POC compared by medium volume were statistically significant (p = 0.0003 at 20% and p = 0.001 at 5%). Glycosaminoglycan production and aggrecan gene expression were most promoted when cultured in moderately
low POC, 1,000 μl (2,960-μm depth) at 20% O2 and 500 μl (1,480-μm depth) at 5% O2 in 12-well culture dishes. We demonstrate that medium volume and oxygen concentration in the incubator affect not only POC
but also chondrogenic differentiation. 相似文献
8.
Three fenamates—niflumic, flufenamic and mefenamic acids—were tested for effects on substrate-induced currents of glutamate
and glycine transporters (EAAT1, EAAT2, GLYT1b and GLYT2a) expressed in Xenopus laevis oocytes. All fenamates inhibited EAAT1 currents; 100 μM flufenamic acid produced the most inhibition, decreasing the I
max by 53 ± 4% (P < 0.001). EAAT2 currents were less sensitive, but 100 μM flufenamic acid inhibited the I
max by 34 ± 5% (P = 0.006). All fenamates inhibited GLYT1b currents; 100 μM flufenamic acid produced the most inhibition, decreasing the I
max by 61 ± 1% (P < 0.001). At 100 μM, effects on the GLYT2a I
max were mixed: 13 ± 2% inhibition by flufenamic acid (P = 0.002), 30 ± 6% enhancement by niflumic acid (P = 0.002), and no effect by mefenamic acid. Minor effects on substrate affinity suggested non-competitive mechanisms. These
data could contribute to the development of selective transport modulators. 相似文献
9.
N2O, CH4 and CO2 emissions from seasonal tropical rainforests and a rubber plantation in Southwest China 总被引:2,自引:1,他引:1
Christian Werner Xunhua Zheng Janwei Tang Baohua Xie Chunyan Liu Ralf Kiese Klaus Butterbach-Bahl 《Plant and Soil》2006,289(1-2):335-353
The main focus of this study was to evaluate the effects of soil moisture and temperature on temporal variation of N2O, CO2 and CH4 soil-atmosphere exchange at a primary seasonal tropical rainforest (PF) site in Southwest China and to compare these fluxes with fluxes from a secondary forest (SF) and a rubber plantation (RP) site. Agroforestry systems, such as rubber plantations, are increasingly replacing primary and secondary forest systems in tropical Southwest China and thus effect the N2O emission in these regions on a landscape level. The mean N2O emission at site PF was 6.0 ± 0.1 SE μg N m−2 h−1. Fluxes of N2O increased from <5 μg N m−2 h−1 during dry season conditions to up to 24.5 μg N m−2 h−1 with re-wetting of the soil by the onset of first rainfall events. Comparable fluxes of N2O were measured in the SF and RP sites, where mean N2O emissions were 7.3 ± 0.7 SE μg N m−2 h−1 and 4.1 ± 0.5 SE μg N m−2 h−1, respectively. The dependency of N2O fluxes on soil moisture levels was demonstrated in a watering experiment, however, artificial rainfall only influenced the timing of N2O emission peaks, not the total amount of N2O emitted. For all sites, significant positive correlations existed between N2O emissions and both soil moisture and soil temperature. Mean CH4 uptake rates were highest at the PF site (−29.5 ± 0.3 SE μg C m−2 h−1), slightly lower at the SF site (−25.6 ± 1.3 SE μg C m−2 h−1) and lowest for the RP site (−5.7 ± 0.5 SE μg C m−2 h−1). At all sites, CH4 uptake rates were negatively correlated with soil moisture, which was also reflected in the lower uptake rates measured in the watering experiment. In contrast to N2O emissions, CH4 uptake did not significantly correlate with soil temperature at the SF and RP sites, and only weakly correlated at the PF site. Over the 2 month measurement period, CO2 emissions at the PF site increased significantly from 50 mg C m−2 h−1 up to 100 mg C m−2 h−1 (mean value 68.8 ± 0.8 SE mg C m−2 h−1), whereas CO2 emissions at the SF and RP site where quite stable and varied only slightly around mean values of 38.0 ± 1.8 SE mg C m−2 h−1 (SF) and 34.9 ± 1.1 SE mg C m−2 h−1 (RP). A dependency of soil CO2 emissions on changes in soil water content could be demonstrated for all sites, thus, the watering experiment revealed significantly higher CO2 emissions as compared to control chambers. Correlation of CO2 emissions with soil temperature was significant at the PF site, but weak at the SF and not evident at the RP site. Even though we demonstrated that N and C trace gas fluxes significantly varied on subdaily and daily scales, weekly measurements would be sufficient if only the sink/ source strength of non-managed tropical forest sites needs to be identified. 相似文献
10.
Variation of chromophoric dissolved organic matter and possible attenuation depth of ultraviolet radiation in Yunnan Plateau lakes 总被引:2,自引:0,他引:2
The increase of ultraviolet radiation (UVR, 280–400 nm) caused by stratospheric ozone depletion has profound effects on aquatic
ecosystems. High-altitude lakes in the Yunnan Plateau are exposed to high intensities of UVR and contain low concentrations
of chromophoric dissolved organic matter (CDOM). Thirty-eight lakes in the Yunnan Plateau with elevations from 1291 to 3809
m above sea level were investigated to study CDOM concentrations and possible effects of UVR on the lake ecosystem. The attenuation
of UVR in the Yunnan Plateau lakes was calculated from the absorption coefficient of CDOM based on an empirical relationship
from lakes in the Alps and Pyrenees mountains. Absorption coefficients [α(λ)] at 320 nm [α(320)] ranged from 0.52 to 14.05 m−1 (mean ± standard deviation, 4.40 ± 3.85 m−1) and at 380 nm [α(380)] from 0.05 to 4.51 m−1 (1.40 ± 1.30 m−1). The exponential slope coefficient for the relationship of wavelength to α(λ) ranged from 16.2 to 41.4 μm−1 (21.74 ± 4.93 μm−1) over the 280–400 nm interval. Normalized fluorescence emission (NFLU) at 450 nm from an excitation wavelength of 355 nm,
F
n(355), averaged 7.93 ± 3.22 NFLU. A significant positive relationship was found between α(355) and F
n(355). The estimated diffuse attenuation coefficients of UV-B (320 nm) and UV-A (380 nm) ranged from 0.55 to 15.77 m−1 and from 0.24 to 6.73 m−1; the corresponding 1% attenuation depths ranged from 0.29 to 8.44 m and from 0.68 to 19.12 m. Twenty-five of 38 lakes had
1% UV-B attenuation depths of 1.5 m or more. The median 1% attenuation depth was 28.8% of the sampling depth for UV-B radiation
and 60% for UV-A. In addition to CDOM, chlorophyll α (Chla) and total suspended matter (TSM) also may contribute to attenuation of UVR. 相似文献
11.
Picophytoplankton biomass, community structure and productivity in the Great Astrolabe Lagoon, Fiji 总被引:4,自引:0,他引:4
Phytoplankton biomass, community structure and productivity of the Great Astrolabe lagoon and surrounding ocean were studied
using measurements of chlorophyll concentration and carbon uptake. The contribution of picophytoplankton to biomass, productivity
and community structure was estimated by size fractionation, 14C-incubation and flow cytometry analysis. Picoplankton red fluorescence was demonstrated to be a proxy for chlorophyll <3 μm.
Consequently, the percentage contribution to chl a<3 μm from each picoplankton group could be calculated using regression estimated values of ψ
i
(fg chl a per unit of red fluorescence). In the lagoon, average chlorophyll concentration was 0.8 mg m-3 with 45% of phytoplankton <3 μm. Primary production reached 1.3 g C m-2 day-1 with 53% due to phytoplankton <3 μm. Synechococcus was the most abundant group at all stations, followed by Prochlorococcus and picoeukaryotes. At all stations, Prochlorococcus represented less than 4% of the chl a <3 μm, Synechococcus between 85 and 95%, and Picoeukaryotes between 5 and 10%. In the upper 40 m of surrounding oceanic waters, phytoplankton
biomass was dominated by the >3 μm size fraction. In deeper water, the <1 μm size fraction dominated. Prochlorococcus was the most abundant picoplankton group and their contributions to the chlorophyll a<3 μm were close to that of the picoeukaryotes (50% each).
Accepted: 27 May 1999 相似文献
12.
XiuFang Weng ZhiHui Liang XiaoLing Lu MaoHua Zhong ShengJun Lu CaiE Zhang Jing Deng XiongWen Wu FeiLi Gong 《中国科学:生命科学英文版》2007,50(2):203-211
The role of the bound peptide in alloreactive T-cell recognition is controversial, ranging from pep-tide-independent to peptide-specific recognition of alloreactive T-cells. The aim of this study is to find the evidence that there exist peptide/MHC complex (pMHC)-specific CTLs among alloreactive T cells generated with long-term mixed lymphocytes culture (LTMLC). A single pMHC was manipulated by loading the TAP-defective, HLA-A2 expressing T2 cells with a viral peptide (LMP2A426-434) or a self-peptide (Tyr369-377). The PBLs samples from 4 HLA-A2 positive (HLA-A2 ve) and 4 HLA-A2 negative (HLA-A2-ve) donors were included in this study. The HLA-A2 ve PBL co-cultured with the LMP2A426-434 pulsed T2 (T2/LMP) stands for the nominal T-cell response to a viral antigen, and the HLA-A2-ve PBLs co-cultured with the Tyr369-377 pulsed T2 (T2/Tyr) for alloreactive T-cell response to an allogeneic antigen. The specificity of the expanded CTLs after the LTMLC was detected by their specific cytotoxicity and binding ability to specific pMHC-tetramer. An HLA-A2 restricted, HIV peptide (Gag77-85)was included for control. The cultural bulk of HLA-A2 ve PBLs with the T2/LMP showed an elevated specific cytotoxicity against the T2/LMP compared to that against the T2/HIV (26.52%±3.72% vs 7.01%±0.87%, P<0.001), and an increased frequency of binding to LMP-tetramer compared to that binding to HIV-tetramer (0.98%±0.33% vs 0.05%±0.01%, P=0.0014). The cultural bulk of HLA-A2-ve PBLs with the T2/Tyr showed a more active cytotoxicity against the T2/Tyr than that against T2/HIV (28.07%±2.58% vs 6.87%±0.01 %, P<0.001), and a higher frequency of binding to the Tyr-tetramer than that binding to the HIV-tetramer (0.88%±0.3% vs 0.06%±0.03%, P=0.0018). Our results indicate that the LTMLC is able to expand the viral antigen-specific CTLs as well as allogeneic antigen-specific CTLs. A relatively large proportion of alloreactive CTLs should be pMHC-specific, i.e., the specificity of the alloreactive lines depends on both the bound peptide and the allotype of MHC. Our observations support the hypothesis that the cumulative effect of T cells specific to each peptide epitope could account for the strength and diversity of the alloresponse. The method using manipulated pMHC and the LTMLC to generate pMHC-specific, alloreactive CTLs is of potential importance for adoptive T-cell immunotherapy. 相似文献
13.
Howard J. Green M. E. Burnett C. D’Arsigny S. Iqbal J. Ouyang K. A. Webb D. E. O’Donnell 《Journal of molecular histology》2009,40(1):41-51
Chronic obstructive pulmonary disease (COPD) is known to elicit intrinsic abnormalities in male skeletal muscle. However,
it is unclear to what extent these changes occur in women and whether they are fiber-type specific. We investigated fiber-type
specific differences in selected histochemical properties in muscle obtained from women with moderate to severe COPD compared
to healthy control (CON) women. Tissue was obtained from the vastus lateralis in five COPD patients (age 66.9 ± 2.6 years;
FEV1 = 43 ± 7%) and eight CON (age 68 ± 4.9 years; FEV1 = 113 ± 4.2%). Compared to CON, the distribution (30.6 ± 5.2 vs. 57.9 ± 4.6%) and cross sectional area of type I (CSA, 5660 ± 329
vs. 3586 ± 257 μm2) and type IIA (2770 ± 302 vs. 2099 ± 206 μm2) were lower (P < 0.05) and higher (P < 0.05), respectively, in COPD. Disease state did not alter either the distribution or CSA of the IIA, IIAX or type X subtypes.
Although differences were found between fiber types in the number of capillary contacts (n) (I > IIAX, IIX; IIA > IIX) and the capillaries per CSA (μm210−3) (I < IIA, IIAX, IIX), no differences were found between CON and COPD. Succinic dehydrogenase activity and sarcoplasmic reticulum
(SR) Ca2+-ATPase activity, measured photometrically (OD units), were higher (P < 0.05), and lower (P < 0.05), respectively, in type I compared to the type II fiber subtypes. These properties were not altered with COPD. COPD
in females is accompanied by a higher percent of type II fibers, a larger CSA of type I and type IIA fibers, both of which
occur in the absence of differences in oxidative potential and the potential for SR Ca2+-sequestration. 相似文献
14.
Solenov EI Nesterov VV Baturina GS Khodus GR Ivanova LN 《European biophysics journal : EBJ》2003,32(7):614-619
We report a novel approach for assessing the volume of living cells which allows quantitative, high-resolution characterization
of dynamic changes in cell volume while retaining the cell functionality. The aim of this study was to evaluate the short-term
effect of vasopressin on basolateral cell surface water permeability in the outer medullary collecting duct (OMCD). The permeability
of the basolateral cell membrane was determined in the tubules where the apical membrane was blocked with oil injected into
the lumen. The apparent coefficient of water permeability (P
f) was evaluated by measuring the cell swelling after the step from hypertonic to isotonic medium (600 mosm to 300 mosm). Desmopressin
(dDAVP) induced an increase of the basolateral P
f from 113.7±8.5 μm/s in control cells to 186.6±11.4 μm/s in micro-dissected fragments of the OMCD incubated in vitro (10−7 M dDAVP, 30 min at 37 °C) (P<0.05). Mercury caused pronounced inhibition of basolateral water permeability (26.0±6.9 μm/s; P<0.05). The effect of mercury (1.0 mM HgCl2) was reversible: after washing the fragments with PBS for 20 min, P
f values were restored to the control levels (125.0±9.5 μm/s). The results of the study indicate the existence of a mechanism
controlling the osmotic water permeability of the basolateral cell membrane in the OMCD epithelium. 相似文献
15.
Muscarinic m3 receptor-mediated changes in cytosolic Ca2+ concentration ([Ca2+]l) occur by activation of Ca2+ release channels present in the endoplasmic reticulum membrane and Ca2+ entry pathways across the plasma membrane. In this report we demonstrate the coupling of m3 muscarinic receptors to the activation
of a voltage-insensitive, cation-selective channel of low conductance (3.2 ± 0.6 pS; 25 mm Ca2+ as charge carrier) in a fibroblast cell line expressing m3 muscarinic receptor clone (A9m3 cells). Carbachol (CCh)-induced
activation of the cation-selective channel occurred both in whole cell and excised membrane patches (CCh on the external side),
suggesting that the underlying mechanism involves receptor-channel coupling independent of intracellular messengers. In excised
inside-out membrane patches from nonstimulated A9m3 cells GTP (10 μm) and GDP (10 μm) activated cation-selective channels with conductances of approximately 4.3 and 3.3 pS, (25 mm Ca2+ as charge carrier) respectively. In contrast, ATP (10 μm), UTP (10 μm) or CTP (10 μm) failed to activate the channel. Taken together, these results suggest that carbachol and guanine nucleotides regulate the
activation of a cation channel that conducts calcium.
Received: 14 November 1996/Revised: 4 April 1997 相似文献
16.
Checo Colón-Gaud Scot Peterson Matt R. Whiles Susan S. Kilham Karen R. Lips Cathy M. Pringle 《Hydrobiologia》2008,603(1):301-312
Allochthonous inputs of detritus represent an important energy source for streams in forested regions, but dynamics of these
materials are not well studied in neotropical headwater streams. As part of the tropical amphibian declines in streams (TADS)
project, we quantified benthic organic matter standing stocks and organic seston dynamics in four Panamanian headwater streams,
two with (pre-amphibian decline) and two without (post-decline) healthy amphibian assemblages. We also measured direct litterfall
and lateral litter inputs in two of these streams. Continuous litterfall and monthly benthic samples were collected for 1 year,
and seston was collected 1–3 times/month for 1 year at or near baseflow. Direct litterfall was similar between the two streams
examined, ranging from 934–1,137 g DM m−2 y−1. Lateral inputs were lower, ranging from 140–187 g DM m−1 y−1. Dead leaves (57–60%), wood (24–29%), and green leaves (8–9%) contributed most to inputs, and total inputs were generally
higher during the rainy season. Annual habitat-weighted benthic organic matter standing stocks ranged from 101–171 g AFDM
m−2 across the four study reaches, with ∼4 × higher values in pools compared to erosional habitats. Total benthic organic matter
(BOM) values did not change appreciably with season, but coarse particulate organic matter (CPOM, >1 mm) generally decreased
and very fine particulate organic matter (VFPOM, 1.6–250 μm) generally increased during the dry season. Average annual seston
concentrations ranged from 0.2–0.6 mg AFDM l−1 (fine seston, <754 μm >250 μm) and 2.0–4.7 mg AFDM l−1 (very fine, <250 μm >1.6 μm), with very fine particles composing 85–92% of total seston. Quality of fine seston particles
in the two reaches where tadpoles were present was significantly higher (lower C/N) than the two where tadpoles had been severely
reduced (P = 0.0028), suggesting that ongoing amphibian declines in this region are negatively influencing the quality of particles
exported from headwaters. Compared to forested streams in other regions, these systems receive relatively high amounts of
allochthonous litter inputs but have low in-stream storage.
Handling editor: J. Padisak 相似文献
17.
Kh. S. Vishniakova I. I. Kireev A. Ya. Dunina-Barkovskaya 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2011,5(4):355-363
Cell culture density is shown to alter the parameters characterizing phagocytic activity of cells in vitro. Phagocytosis index
(PI, mean number of beads per cell in the bead-containing population) and phagocytosis percent (PP, percentage of bead-containing
cells in cell population under study) for IC-21 macrophages incubated in the presence of non-opsonized 2-μm fluorescent latex
beads were determined using fluorescent microscopy and ImageJ software specially adapted for the purpose. Under control conditions
(DMEM without serum), increase in cell culture density was accompanied with a decrease of both parameters of the phagocytic
activity. At a mean density of 4 cells/105 μm2 (9 cells per a viewfield) PI was 7.1 ± 0.2 beads/cell and at 20 cells/105 μm2 (40 cells per a viewfield) PI dropped to 4.6 ± 0.1 beads/cell. PP was less sensitive, varied in the range of 95–100% but
also decreased as the cell density grew. At any density, PI was 1.5–2 times higher than the expected value (number of beads
per μm2 × cell contour area); apparently this divergence can be accounted for by cell locomotion and capture of a larger number of
beads than could drop onto a motionless cell with a constant contour area. Increase in cell density was also accompanied by
a decrease of the cell contour area (S
c), which amounted to 750 ± 16 μm2 at a density of 4 cells/105 μm2 and 346 ± 4 μm2 at a density of 20 cells/105 μm2. As the bead concentration was the same in all experiments, density-dependent decrease in PI and PP may be related with the
observed decrease in cell contour area. Yet, the bead number per cell area unit (PI/S
c) was bigger at higher density and PI/S
c was higher in cells with smaller S
c. Thus, individual (specific) activity of the cells did not lessen with an increase of the cell culture density in the range
studied (4–20 cells/105 μm2). Reduction of the cell contour area may reflect alteration in cell adhesion to the substrate as well as competitive relations
between adhesion and phagocytic processes. The data obtained imply that cell culture density has to be controlled as a factor
notably altering the phagocytic activity parameters. The effects of serum, methyl-β-cyclodextrin, and carbenoxolon reported
earlier [Golovkina et al. 2009. Biol membrany. 26 (5), 379–386] are re-evaluated and confirmed here. 相似文献
18.
Smooth muscle cells isolated from the secondary and tertiary branches of the rabbit mesenteric artery contain large Ca2+-dependent channels. In excised patches with symmetrical (140 mm) K+ solutions, these channels had an average slope conductance of 235 ± 3 pS, and reversed in direction at −6.1 ± 0.4 mV. The
channel showed K+ selectivity and its open probability (P
o
) was voltage-dependent. Iberiotoxin (50 nm) reversibly decreased P
o
, whereas tetraethylammonium (TEA, at 1 mm) reduced the unitary current amplitude. Apamin (200 nm) had no effect. The channel displayed sublevels around 1/3 and 1/2 of the mainstate level. The effect of [Ca2+] on P
o
was studied and data fitted to Boltzmann relationships. In 0.1, 0.3, 1.0 and 10 μm Ca2+, V
1/2 was 77.1 ± 5.3 (n= 18), 71.2 ± 4.8 (n= 16), 47.3 ± 10.1 (n= 11) and −14.9 ± 10.1 mV (n= 6), respectively. Values of k obtained in 1 and 10 μm [Ca2+] were significantly larger than that observed in 0.1 μm [Ca2+]. With 30 μm NS 1619 (a BKCa channel activator), V
1/2 values were shifted by 39 mV to the left (hyperpolarizing direction) and k values were not affected. TEA applied intracellularly, reduced the unitary current amplitude with a K
d
of 59 mm. In summary, BKCa channels show a particularly weak sensitivity to intracellular TEA and they also display large variation in V
1/2 and k. These findings suggest the possibility that different types (isoforms) of BKCa channels may exist in this vascular tissue.
Received: 22 December 1997/Revised: 27 March 1998 相似文献
19.
Codium fragile (Suringar) Hariot is an edible green alga farmed in Korea using seed stock produced from regeneration of isolated utricles
and medullary filaments. Experiments were conducted to reveal the optimal conditions for nursery culture and out-growing of
C. fragile. Sampling and measurement of underwater irradiance were carried out at farms cultivating C. fragile at Wando, on the southwestern coast of Korea, from October 2004 to August 2005. Growth of erect thalli and underwater irradiance
were measured over a range of depths for three culture stages. During the nursery cultivation stage (Stage I), growth rate
was greatest at 0.5 m depth (0.055 ± 0.032 mm day−1), where the average midday irradiance over 60 days was 924 ± 32 μmol photons m−2 s−1. During the pre-main cultivation stage (Stage II), the greatest growth rate occurred at a depth of 2 m (0.113 ± 0.003 mm day−1) with an average irradiance of 248 ± 116 μmol photons m−2 s−1. For the main cultivation stage (Stage III) of the alga, thalli achieved the greatest increase in biomass at 1 m depth (7.2 ± 1.0 kg
fresh wt m−1). These results suggest that optimal growth at each cultivation stages of C. fragile could be controlled by depth of cultivation rope. 相似文献
20.
The protein bCblC (bCblCpro) is a bovine homolog of a human B12 trafficking chaperone that is responsible for the processing of vitamin B12 and its escorted delivery in intracellular B12 metabolism. In this study, we found that bCblCpro is highly thermolabile with a T
m = 42.0 ± 0.2 °C as shown for the human homolog, suggesting thermal regulation of these proteins. Binding of the reduced form
of glutathione (GSH) that is a predominant cellular thiol increased the T
m of bCblCpro from 42 °C to ~45 °C (ΔT
m max = 3.1 ± 0.2 °C and AC50 = 2.1 ± 0.5 mM). Binding of vitamin B12 and its derivatives also stabilized bCblCpro increasing the T
m to a different extent and vitamin B12 (cyanocobalamin, CNCbl) was the least efficient (ΔT
m max = 4.3 ± 0.3 °C and AC50 = 291 ± 36 μM). However, the stabilizing effect of CNCbl was significantly greater for GSH-bound bCblCpro (ΔT
m max = 12.8 ± 0.6 °C and AC50 = 9.3 ± 1.6 μM) than for GSH-free bCblCpro. In addition, the stabilizing effect of GSH was also greater for CNCbl-bound bCblCpro
(ΔT
m max = 9.3 ± 0.3 °C and AC50 = 57.0 ± 6.8 μM). Limited proteolysis revealed that thermal stabilization of bCblCpro is derived from conformational changes
of the protein induced by binding of the ligands. The results in this study indicate that GSH cooperates with vitamin B12 in thermal stabilization of bCblCpro and is a positive regulator of the protein. 相似文献